1. Field
An aspect of the present invention relates to an electronic device having a heat sink and a method for coping with static electricity.
2. Description of the Related Art
In recent, heat values during operation have been increasing every year since semiconductor devices having a high process speed (e.g., CPU) are demanded for digital media apparatuses such as a digital TV. Excessively heated high-temperature semiconductor devices may malfunction. Accordingly, semiconductor devices with high power consumption and high heat values have been provided with a high sink. Generally, heat sinks are made of metal having high thermal conductivity such as aluminum, and are fixed onto semiconductor devices.
In JP-A-2000-183256, a structure where a heat sink is pressed and fixed onto a semiconductor device using a spring member is described.
Since the heat sink is a conductive element and may be the route of electric charges, the heat sink may serve as a discharge place of static electricity and noise. Accordingly, when electrostatic discharge (ESD) occurs, static electricity having no place to go are discharged to a terminal or the like of the neighboring semiconductor device through the heat sink, and thus the neighboring semiconductor device may be seriously damaged (destruction, malfunction, etc. of semiconductor device).
To avoid the ESD problem, the heat sink has been connected to a ground potential (GND) (see JP-A-2006-80453). According to this technique, since the static electricity discharged to the heat sink flows into the GND having electric potential lower than that of the semiconductor device, the semiconductor device is hardly damaged.
An ESD countermeasure is important in addition to the heat radiation countermeasure when the heat sink is provided, as described above. However, when the heat sink is connected to the GND as described above, undesired radiation may increase. That is, even if the heat sink is connected to the GND, it may be hard to say that the heat sink is ideally connected to the GND since the GND around the semiconductor device has relatively large noise. Therefore, undesired radiation occurs by connecting the heat sink to the GND, and electromagnetic interference with external electronic devices (e.g., radio, etc.), such as noise and the like may be generated. In an area where undesired radiation is strictly controlled, the standard may fail to be satisfied.